Impeller Assembly

ABSTRACT

An impeller assembly including a rim plate defining a plurality of blades and the backplate defining a blade interlock structure for aligning and coupling the plates together. The rim plate defines a plurality of fluid-engaging blades. The interlock structure includes a plurality of tine-shaped interlocks extending from the backplate. The interlock structure also includes a plurality of channel sections engaging the blades. Each blade of the impeller may engage the interlock structure in a saddle manner. The backplate is defined by areas of reduced thickness allowing outer portions of the backplate to flex (rotate) toward further contact with the rim plate.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/298,138, filed Jan. 25, 2010, and incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to impeller devices for moving fluids, particularly air. The invention further relates to the assembly of components to manufacture an impeller device.

BACKGROUND OF THE INVENTION

Impellers are a rotating component of a pump, fan, or other device that moves fluids. Impellers transfer energy from a prime mover to a fluid. A radial impeller forces the fluid generally outwards from the center of rotation. There are several types of impellers that are commonly found in various operations. One type of impeller uses one shroud which is a backplate mounted on the side of the blades opposite to the side of the impeller where the air enters. A second type uses two shrouds, a backplate and a cone that is mounted on the side of the blades where the air enters the impeller. A third type uses a single backplate in the center of the blades and two cones on the ends of the blades.

Impellers that have both a backplate and a wheel cone typically have blades between the plates. In many applications, the blades are formed integrally with one or both rim plates. Fluid to be pumped is introduced into the impeller housing at one side thereof. The shaft rotates so as to rotate the impeller thereby creating regions of high and low pressure within the impeller housing and impelling fluid through the assembly.

Both impellers with cones and without cones have advantages and disadvantages relative to each other. It is less expensive to manufacture impellers without cones but they require tighter assembly tolerances for fans with low specific speeds. Impellers with cones are significantly more expensive to manufacture as they require welding or other time intensive manufacturing processes to form them. Further, the welding or connection point of the cone to the impeller is often the weakest link of the impeller. However, they are usually more efficient than impellers without cones especially for impellers with low specific speeds.

Impellers may be characterized as open-faced or closed-face. Open faced impellers work well in many applications that produce a high volume of air at low to medium pressures. The closed face impeller has advantages in low flow medium to high pressure applications which includes the vacuum fans in known floor sweepers and scrubbers. That is because the open face of an open faced impeller does not form a complete seal against the fan housing and so air leaks by that face. On a narrow open faced fan, the leak can be a significant portion of the airflow and so it will be less efficient than a wide open faced impeller or a closed face impeller. One way to maximize the efficiency of an open faced impeller is to maintain a very small gap between the housing wall and open side of the impeller. Keeping a small gap requires higher precision parts, more difficult assembly of the parts, and designs that accommodate thermal changes. These factors all raise the cost of the overall design. Today most closed face impellers are made in pieces that are attached by any combination of welding, bolting, riveting, staking, or gluing. A single piece closed face impeller can be made but requires very complicated tooling and manufacturing procedures.

An example of a closed face impeller 100, such as the fan used in the Tennant Model 530 sweeper, is shown in FIGS. 14-16. FIG. 14 shows the backplate 102 of the impeller 100. This is the part of the impeller 100 that is driven by the motor and moves air. FIG. 15 shows the rim plate 104 of impeller 100. The rim plate 104 is glued or welded to the backplate 102, seals one side of the blades 106, and is driven by the backplate 102. FIG. 16 is the impeller 100 comprised of backplate 102 and rim plate 104 as assembled together. When this type of impeller 100 operates, there is a zone of high stress near the intersection of the blades 106 and the rim plate 104.

A high stress zone exists in the area where the blades 106 are welded or glued to the rim plate 104. Since that joint is often the weakest part of the impeller 100, the highest stress is in the weakest part of the impeller 100. To overcome this limitation, a method to assemble fans was disclosed in U.S. Ser. No. 12/043,907, entitled Impeller Assembly and Method of Using, and incorporated by reference herein. That application describes a way to assemble fans by snapping them together.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to an apparatus and method for manufacturing a closed faced impeller assembly. In one example, a pair of plates is provided with one or both of the plates being adapted for coupling to a shaft means. A rim plate having a concentric aperture is adapted to allow fluid to enter the blade assembly. The rim plate is provided with a plurality of blades for engaging a fluid. Preferably the blades are formed integrally with a rim plate. The other plate, the backplate, is provided with a plurality of blade interlocks adapted to couple the plates together and provide at least some structure suitable for transferring torque between the blade plates.

The backplate may include a base having areas of reduced thickness allowing outer portions of the backplate to flex (rotate) toward further contact with the rim plate during high speed rotation. The areas of reduced thickness may be positioned between tine-shaped portions of the interlock structure and channel-shaped portions of the interlock structure.

Applicant has found that impellers of the present invention can operate with significantly higher tip speeds and generate more pressure than comparable prior art closed-face impeller designs.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an impeller assembly according to one embodiment of the present invention.

FIG. 2 shows the backplate portion of the impeller assembly of FIG. 1.

FIG. 3 shows a detailed portion of the backplate of FIG. 2.

FIG. 4 shows the backplate portion of FIG. 1

FIG. 5 shows the rim plate portion of the impeller assembly of FIG. 1

FIG. 6 shows another view of the rim plate of FIG. 5.

FIG. 7 shows the impeller assembly of FIG. 1.

FIG. 8 shows a cross-sectional view of the impeller assembly of FIG. 7.

FIG. 9 shows another cross-sectional view of the impeller assembly of FIG. 7.

FIG. 10 shows yet another cross-sectional view of the impeller assembly of FIG. 7.

FIG. 11 shows a cross-sectional view of the backplate of FIG. 2

FIG. 12 shows another cross-sectional view of the backplate of FIG. 2.

FIG. 13 shows a cross-sectional view of the impeller assembly of FIG. 1 attached to a drive shaft.

FIG. 14 shows a backplate portion of an impeller assembly of the prior art.

FIG. 15 shows a cover portion of an impeller assembly of the prior art.

FIG. 16 shows the backplate portion and cover portion of FIGS. 14-15 to define a impeller assembly of the prior art.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, FIG. 1 illustrates an impeller assembly 100 according to one example of the present invention. Impeller assembly 100 includes a backplate 10, an upper rim plate 12 and a plurality of blades 14 between the plates 10, 12. In the context of this specification, the terms “upper” and “lower” do not indicate a particular orientation of the components or assembly, or a particular relative position, but are employed for distinguishing purposes.

During impeller assembly 100 operation, fluid is moved from the center of the impeller 100 to the outer edge of the impeller via passageways 13 defined by the blades 14 between the rim plate 12 and the backplate 10. Blades 14 may be radially aligned (as shown in this example) or involute (in another embodiment) and serve to create regions of high and lower pressure within the impeller assembly during impeller operation, so as to impel fluid through the impeller assembly 100.

Referring to FIG. 2, blade interlocks 15 of backplate 10 may be formed integrally on an upper surface face of backplate 10. Backplate 10 may be of pressed metal construction or manufactured from a polymeric material. In the illustrated embodiment, at least a portion of the blades 14 are of sufficient height to extend between the backplate 10 and rim plate 12.

Backplate 10 also includes a center hub 22 with blade interlocks 15 extending in a generally radial manner from center hub 22 to an outer edge 26 of backplate 10. Backplate 10 includes a center aperture 28 adapted to receive a drive shaft (not shown). Center aperture 28 may be splined or include other coupling structures useful to transfer torque from a drive shaft to impeller assembly 100.

FIGS. 3-4 are detailed illustrations of backplate 10 of FIG. 2 and illustrates the generally radial nature of the blade interlocks 15 relative to center aperture 28. Central portions of the blade interlocks 15 generally define upwardly-extending tines. Outer portions of the blade interlocks 15 generally define small channels for engaging lower side edges of the blades 14 in saddle-manner.

Referring to FIG. 5, rim plate 12 includes a plurality of apertures 52 through which fluid passes during impeller operation. Center aperture 50 may be splined or include other coupling structures useful to transfer torque from a drive shaft to impeller assembly 100. Center aperture 50 is aligned with center aperture 28 of backplate 10 so as to receive a drive shaft. Center aperture 50 is contained within center hub 51 of rim plate 12.

FIG. 6 shows the underside of rim plate 12. Blades 14 extend from near center aperture 50 outwardly in a radial manner. In the illustrated embodiment, blades 14 are equally spaced from each other. In other embodiments, the spacing between adjacent blades 14 may vary, i.e., the spacing between some blade 14 pairs may be substantially greater than the space between other blade 14 pairs.

FIG. 7 shows the impeller assembly 100 after the rim plate 12 has engaged backplate 10. The rimplate 12 and backplate 10 may be adhered together and/or may be mechanically secured together via mechanical clamping, such as upon the drive shaft by a threaded fastener, etc.

FIGS. 8-10 show various cross-sectional views of the impeller assembly 100. As shown in FIG. 10, the inner blade interlocks 15 are each received between a pair of blades 14. The blade interlocks 15 may contact one or more of the side surfaces of the pair of adjacent blades 14 and outer surface of hub 51.

FIG. 11 shows the backplate 10 in cross-section and illustrates areas 110 having reduced thickness relative to other areas. By reducing the thickness in these areas 110, the rotational forces during operation tend to bias the outer portions of the backplate 10 upperwardly (toward the rim plate 12), as depicted by arrows 120. These forces tend to maintain the backplate 10 and rim plate 12 in close contact during rotation. During high speed rotation, the areas of reduced thickness 110 allow the outer portions of the backplate 10 to flex into greater contact with the rim plate 12. In the illustrated embodiment, the areas 110 of reduced thickness are define by asymmetric thinning of the base of the backplate, e.g., the “removed material” is predominantly located on the lower surface of the base. The thinning of the backplate preferably occurs at the lower surface of the base of the backplate (furthest away from the rim plate 12), so as to cause the outer portions of the backplate 12 to flex as shown by arrows 120 toward increased contact with the rim plate 12.

FIG. 12 is a cross-sectional view of backplate 10 taken generally through its center.

FIG. 13 shows the impeller assembly 100 attached to a drive shaft 140. A threaded fastener 142 is used to secure the impeller assembly 100 at a threaded end 144 of drive shaft 140.

During assembly of impeller 100, backplate 10 and rim plate 12 are aligned and brought together so that lower edges of blades 14 engage blade interlocks 15.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. 

1. An impeller assembly comprising: a generally circular rim plate having a center hub for connection to a drive shaft; a generally circular backplate; a plurality of blades between the rim plate and the backplate, with said plurality of blades extending from the rim plate; and a blade interlock structure, said blade interlock structure including blade interlocks engaging sides of said plurality of blades, said blade interlock structure providing a torque coupling between the rim plate and the backplate.
 2. The impeller assembly of claim 1 with said blade interlock structure wherein the blade interlocks are radially-aligned relative to a backplate center.
 3. The impeller assembly of claim 1 wherein the plurality of blades extend from the center hub of the rim plate.
 4. The impeller assembly of claim 3 wherein the center hub includes an aperture for receiving the drive shaft to rotate the impeller assembly during operation.
 5. The impeller assembly of claim 1 wherein the backplate includes an area of reduced thickness between a center of the backplate and an outer edge of the backplate, with said area of reduced thickness causing the backplate to flex toward the rim plate.
 6. The impeller assembly of claim 1 wherein the blade interlock structure includes a central blade interlock structure separated from a radially-outer interlock structure.
 7. The impeller assembly of claim 6 wherein the radially-outer interlock structure defines a plurality of channels, with each channel being sized to engage side surfaces of one of the plurality of blades.
 8. The impeller assembly of claim 6 wherein the central blade interlock structure includes a plurality of tines.
 9. The impeller assembly of claim 8 wherein the plurality of tines engage the blades of the impeller.
 10. An impeller assembly comprising: a generally circular rim plate having a center hub for connection to a drive shaft; a generally circular backplate; a plurality of blades between the rim plate and the backplate, with said plurality of blades extending from the rim plate; and a blade interlock structure on said backplate for engaging the plurality of blades, said blade interlock structure providing a coupling between the plurality of blades and the backplate.
 11. The impeller assembly of claim 10 further comprising an interlock structure of a plurality of radially-aligned blade interlocks.
 12. The impeller assembly of claim 10 wherein the plurality of blades extend from the center hub of the rim plate.
 13. The impeller assembly of claim 12 wherein the center hub includes an aperture for receiving the drive shaft to rotate the impeller assembly during operation.
 14. The impeller assembly of claim 10 wherein the backplate includes an area of reduced thickness between a center of the backplate and an outer edge of the backplate, with said area of reduced thickness causing the backplate to flex toward the rim plate.
 15. The impeller assembly of claim 10 wherein the blade interlock structure includes a central blade interlock structure separated from a radially-outer interlock structure.
 16. The impeller assembly of claim 15 wherein the radially-outer interlock structure defines a plurality of channels, with each channel being sized to engage side surfaces of one of the plurality of blades.
 17. The impeller assembly of claim 15 wherein the central blade interlock structure includes a plurality of tines.
 18. The impeller assembly of claim 17 wherein the plurality of tines engage the blades of the impeller.
 19. An impeller assembly comprising: a generally circular rim plate having a center hub for connection to a drive shaft; a generally circular backplate having a base with an area of reduced thickness between a center axis of the backplate and an outer edge, said area of reduced thickness allowing an outer portion of the backplate to flex toward further contact with the rim plate during rotation of the impeller assembly; a plurality of blades between the rim plate and the backplate, with said plurality of blades extending from the rim plate; and a blade interlock structure, said blade interlock structure including interlocks engaging sides of said plurality of blades, said blade interlock structure providing a torque coupling between the rim plate and the backplate.
 20. The impeller assembly of claim 19 wherein the blade interlock structure includes a plurality of tines extending toward the rim plate and a plurality of channel sections, with the area of reduced thickness being positioned between the plurality of tines and the plurality of channel sections. 